I see an interesting premise in there, but I'm not sure exactly how to take advantage of it in an RPG. Still, it has possibility.
Well, I guess the idea is-- kinda like a twist on the sandbox campaign.
You have the campaign map already established with it's locations. The players are able to explore the area, discover dungeons and encounter areas and whatever. But by freeing up travel between known cities or whatever, you get to explore more of the map.
So for example, lets say we're using the Forgotten Realms campaign map. It's that poster sized thingy. The character start out in Moonsea or whatever and have some adventures where they travel from there to a neighboring location. I want to just allow the party to say "next we want to travel to here" and point at any
previously visted 'town' location on the map and have the option to either:
A. Travel there normally. In the way I run things thats 4 encounter checks per day, plus some resource accounting (food, etc).
or
B. Just handwave the travel part. Just account for some time spent travelling, and the resources at a standardized scale-- something like the "Upkeep" costs on Living Greyhawk. This is actually quite a bit similar to Living Greyhawk's travel rules because the goal is the same- Players are encouraged to have adventures both within and outside their home region.
Over the course of a longterm campaign this lets the player group get to explore more of the map because they don't have to re-travel the previously visited hexes (but the option is still there, and there may even be a good reason to re-travel them if you haven't discovered the location you want to visit).
At first this won't be a big deal. You are handwaving maybe a couple of days of travel. But by the endof the campaign, it will open any previously visited location int he campaign, which for me would include extraplanar locations, islands, foreign continents, etc. Over the course of a year or so worth of a campaign, this expands an already large playing field in an even larger way. of course it also puts a bit of pressure on the DM to keep worldbuilding as the players keep exploring.